The invention relates to a polymer composition constituted by a modified polymer and a polymer containing at least one reactive function, for the production of tubes or receptacles which have improved mechanical properties using conventional manufacturing equipment.
The invention also relates to polymer mixtures containing a composition of the invention as a compatibilising agent for incompatible polymers.
The prior art, see for example United States patent U.S. Pat. No. 3,373,222 describes polymer compositions containing a polyolefin and a polyamide, which in the presence of a copolymer based on ethylene and acrylic or methacrylic acid have mechanical properties which are superior to those of polyethylene-polyamide mixtures prepared in the absence of an ethylene-acrylic (or methacrylic) acid copolymer. Extrusion or extrusion blow moulding processing methods are used for such compositions.
European patent EP-A-0 015 556 describes a process for the production of objects with a lamellar structure dispersed with compositions containing a polyolefin, a second polyamide type polymer which is incompatible with the polyolefin and an ethylene copolymer containing acid, anhydride or ester groups either in the main chain or as grafts (pendent chains). In that case, the mixture is described as being heterogeneous, with a continuous polyolefinic phase and a dispersed polyamide phase in the form of lamellae oriented in the plane of the wall of the object. Such orientation is obtained by substantial stretching (100% to 500%) of the hot polymer phase in two spatial directions followed by quenching. The thickness of the polyamide lamellae obtained is in the range 0.5 to 50.times.10.sup.-6 meters (see in particular EP-A-0 095 349 and EP-A-0 090 554).
In such a composition type, the agent used to improve the mechanical properties of the mixture obtained is generally a copolymer of ethylene and a fumaric or adipic acid type organic acid (see in particular EP-A-0 095 349, EP-A-0 090 554 and EP-A-0 015 556), also acrylic acid or maleic anhydride (see in particular U.S. Pat. Nos. 3,373,222, 3,373,223, 3,373,224 and 4,444,817).
Polyamide compositions associated with copolymers or terpolymers based on ethylene, an acrylic or methacrylic ester and acrylic or methacrylic acid or maleic anhydride are also known. The presence of copolymers or terpolymers dispersed in a nodular form in a continuous polyamide phase confers on the latter an improved impact strength (see in particular German patent document DE A-2 551 023).
The above references, which represent the current state of the art in the field of thermoplastic resin alloys in general and polyethylene-polyamide mixtures in particular, have led to the interest in using copolymers, i.e., polymers composed of two different monomers, as agents which encourage adhesion between two phases constituted by two incompatible polymers. We have now, surprisingly, discovered that incorporating certain modified polymers into compositions and/or mixtures of incompatible polymers can result in a substantial improvement in physico-chemical and mechanical properties of the composition obtained when compared with binary mixtures.